(a) Field of the Invention
The invention relates to a glueless type connecting structure of a target and a backing plate, and more particularly, to a glueless type connecting structure of a target and a backing plate which directly connects a target with a backing plate without using an adhesive at the joint of the target and the backing plate.
(b) Description of the Related Art
In general, sputtering is used to form a wiring film for a thin film, optical recording and semiconductor field that are used in a liquid crystal panel and an organic electroluminescent panel. The liquid crystal panel and the organic electroluminescent panel are used for a television set, a notebook computer and other monitors.
In sputtering, atoms are separated from a target by applying plasma discharge between a substrate and a target that is a coated material such that an ionized gas hits against the target. The separated atoms are accumulated on the substrate, thereby manufacturing a thin film. The method has the advantage of forming a thin film having the same composition as the target, unlike vacuum depositing or ark ion plating (“AIP”).
The target used in sputtering is generally soldered to a backing plate (also called, cooling plate or support body) which cools and supports the target. The backing plate includes copper or a copper alloy having relatively high thermal conductivity so as to cool the target heated in sputtering.
Regarding soldering between the target and the backing plate (support body), for example, Japanese Patent Application Laid-Open No. 2003-183822 discloses a sputtering target including a target material and a backing plate with a bonding material (e.g., soldered metal) therebetween. The backing plate has a recession for the bonding material and a groove communicating with the recession on the outer circumferential wall of the recession.
This document states that the target does not bend even if the bonding material is solidified and contracted, in the structure. However, the technology of Japanese Patent Application Laid-Open No. 2003-183822 is not directed to prevent separation of the bonding portion (soldered metal) from other elements, and particularly, has a problem in that it is necessary to use a backing plate having a complicated shape.
Japanese Patent Application Laid-Open No. 1996-246144 discloses a technology for preventing a target from bending and cracking and a soldered portion from separating, by disposing plates having larger and lower thermal expansion rates than the sputtering target on opposing surfaces of the backing plate such that the backing plate is interposed between the plates. Interposing the backing plate between the plates prevents the backing plate from bending and provides the sputtering target with the same thermal expansion property as the target to be supported. However, this technology also has a problem in that the structure of the backing plate is complicated.
Japanese Patent Application Laid-Open No. 1998-046327 discloses a method of making a target and a backing plate of an aluminum alloy in order to reduce the difference in a linear expansion rate between the two members. However, the difference in thermal expansion rate is not sufficiently and surely reduced in the composite of the target and the backing plate according to the technology, such that it is difficult to suppress cracks in a soldered metal. Further, when the backing plate includes the same material as the target which including an Al—Nd alloy, the cost is correspondingly increased.